Treasury Department spokesman Tony Sayegh released a letter from Mnuchin to the House Ways and Means Committee that said the agency will first review the request with the Justice Department and won’t be held to any timeline.

In the letter, Mnuchin also mentioned Republican criticism of the tax return request and alleged the request was politically motivated.

Although Mnuchin did not specifically say he would never release the returns, he questioned Congress’ legal right to request the returns.

“The Committee’s request raises serious issues concerning the constitutional scope of congressional investigative authority, the legitimacy of the asserted legislative purpose, and the constitutional rights of American citizens.”

The delay, or eventual refusal to provide Congress with Trump’s tax turns, if that happens, could end up in the courts in a long legal battle and possibly even in the hands of the U.S. Supreme Court.

Trump again refused to turn over the returns on Wednesday and said he was still being audited by the Internal Revenue Service, which he also said on the campaign trail in 2016 when he refused to release his returns then.

Original story: A deadline is set to pass Wednesday for the Internal Revenue Service to hand over six years of President Donald Trump’s tax returns.

It was not clear whether the IRS would comply with the request. The agency’s commissioner, Charles Rettig, and Treasury Secretary Steven Mnuchin told Congress on Tuesday that no decision had yet been made over whether to turn over the information.

“I have said we will comply with the law,” Mnuchin said during a hearing of the House Financial Services Committee. “I have not made a comment one way or the other on whether we will provide the tax returns.”

Six years of Trump’s tax returns were requested last week by House Ways and Means Committee Chairman Rep. Richard Neal, D-Mass., one of four people authorized to request usually private income tax returns under a little-known IRS code.

Section 6103 of the Internal Revenue Code says the Treasury Department secretary “shall furnish … any return or return information” requested by officials, including Neal. The information could then be shared with the House Ways and Means Committee “only when sitting in closed executive session” unless Trump allows for further disclosure.

In his request last week, Neal also asked officials to specify whether the returns he requested had been “under any type of examination or audit” and “the issue(s) under examination.”

Trump has repeatedly declined to release his tax returns, citing an ongoing audit.

“I would love to give them, but I’m not going to do it while I’m under audit,” Trump told reporters Wednesday.

President Trump on releasing his tax returns: "I would love to give them, but I'm not going to do it while I'm under audit." pic.twitter.com/pheeK1epBR

Mnuchin told Congress on Tuesday that his department’s lawyers had discussed releasing the president’s tax returns with the White House counsel’s office, but he said the conversations were “purely informational,” The Associated Press reported. He added that he had not talked to either Trump or the president’s top staff about the request.

Acting White House chief of staff Mick Mulvaney said Sunday that lawmakers will "never" see Trump's returns. But the White House is supposed to stay out of the decision, and Rettig said he's had no contact with anyone there.